verboselogs: Verbose logging level for Python’s logging module

The verboselogs package extends Python’s logging module to add the log levels NOTICE, SPAM, SUCCESS and VERBOSE:

• The NOTICE level sits between the predefined WARNING and INFO levels.
• The SPAM level sits between the predefined DEBUG and NOTSET levels.
• The SUCCESS level sits between the predefined WARNING and ERROR levels.
• The VERBOSE level sits between the predefined INFO and DEBUG levels.

The code to do this is simple and short, but I still don’t want to copy/paste it to every project I’m working on, hence this package. It’s currently tested on Python 2.6, 2.7, 3.4, 3.5, 3.6 and PyPy.

Installation

The verboselogs package is available on PyPI which means installation should be as simple as:

$ pip install verboselogs

There’s actually a multitude of ways to install Python packages (e.g. the per user site-packages directory, virtual environments or just installing system wide) and I have no intention of getting into that discussion here, so if this intimidates you then read up on your options before returning to these instructions ;-).

Usage

It’s very simple to start using the verboselogs package:

>>> import logging, verboselogs
>>> logger = verboselogs.VerboseLogger('verbose-demo')
>>> logger.addHandler(logging.StreamHandler())
>>> logger.setLevel(logging.VERBOSE)
>>> logger.verbose("Can we have verbose logging? %s", "Yes we can!")

Here’s a skeleton of a very simple Python program with a command line interface and configurable logging:

"""
Usage: demo.py [OPTIONS]

This is the usage message of demo.py. Usually
this text explains how to use the program.

Supported options:
  -v, --verbose  make more noise
  -h, --help     show this message and exit
"""

import getopt
import logging
import sys
import verboselogs

logger = verboselogs.VerboseLogger('demo')
logger.addHandler(logging.StreamHandler())
logger.setLevel(logging.INFO)

# Command line option defaults.
verbosity = 0

# Parse command line options.
opts, args = getopt.getopt(sys.argv[1:], 'vqh', ['verbose', 'quiet', 'help'])

# Map command line options to variables.
for option, argument in opts:
    if option in ('-v', '--verbose'):
        verbosity += 1
    elif option in ('-q', '--quiet'):
        verbosity -= 1
    elif option in ('-h', '--help'):
        print __doc__.strip()
        sys.exit(0)
    else:
        assert False, "Unhandled option!"

# Configure logger for requested verbosity.
if verbosity >= 4:
    logger.setLevel(logging.SPAM)
elif verbosity >= 3:
    logger.setLevel(logging.DEBUG)
elif verbosity >= 2:
    logger.setLevel(logging.VERBOSE)
elif verbosity >= 1:
    logger.setLevel(logging.NOTICE)
elif verbosity < 0:
    logger.setLevel(logging.WARNING)

# Your code goes here.
...

If you want to set VerboseLogger as the default logging class for all subsequent logger instances, you can do so using verboselogs.install():

import logging
import verboselogs

verboselogs.install()
logger = logging.getLogger(__name__) # will be a VerboseLogger instance

Pylint plugin

If using the above verboselogs.install() approach, Pylint is not smart enough to recognize that logging is using verboselogs, resulting in errors like:

E:285,24: Module 'logging' has no 'VERBOSE' member (no-member)
E:375,12: Instance of 'RootLogger' has no 'verbose' member (no-member)

To fix this, verboselogs provides a Pylint plugin verboselogs.pylint which, when loaded with pylint --load-plugins verboselogs.pylint, adds the verboselogs methods and constants to Pylint’s understanding of the logging module.

Overview of logging levels

The table below shows the names, numeric values and descriptions of the predefined log levels and the VERBOSE, NOTICE, and SPAM levels defined by this package, plus some notes that I added.

Level	Value	Description	Notes
NOTSET	0	When a logger is created, the level is set to NOTSET (note that the root logger is created with level WARNING).	This level isn’t intended to be used explicitly, however when a logger has its level set to NOTSET its effective level will be inherited from the parent logger.
SPAM	5	Way too verbose for regular debugging, but nice to have when someone is getting desperate in a late night debugging session and decides that they want as much instrumentation as possible! :-)
DEBUG	10	Detailed information, typically of interest only when diagnosing problems.	Usually at this level the logging output is so low level that it’s not useful to users who are not familiar with the software’s internals.
VERBOSE	15	Detailed information that should be understandable to experienced users to provide insight in the software’s behavior; a sort of high level debugging information.
INFO	20	Confirmation that things are working as expected.
NOTICE	25	Auditing information about things that have multiple success paths or may need to be reverted.
WARNING	30	An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected.
SUCCESS	35	A very explicit confirmation of success.
ERROR	40	Due to a more serious problem, the software has not been able to perform some function.
CRITICAL	50	A serious error, indicating that the program itself may be unable to continue running.

Contact

The latest version of verboselogs is available on PyPI and GitHub. The documentation is hosted on Read the Docs. For bug reports please create an issue on GitHub. If you have questions, suggestions, etc. feel free to send me an e-mail at peter@peterodding.com.

License

This software is licensed under the MIT license.

© 2017 Peter Odding.